GATE 2023 BT – Question 49
Aqueous two-phase extraction is used to recover α-amylase from a solution. A polypropylene glycol-dextran mixture is added and the solution separates into upper and lower phases. The partition coefficient is 4.0 and the ratio of upper to lower phase volume is 5.0. The enzyme recovery or yield (in percentage, rounded off to the nearest integer) is ___________.
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: 95
Explanation
In a two-phase extraction, the **partition coefficient** is
$$K=\frac{C_{upper}}{C_{lower}}=4.0,$$
and the **volume ratio** is $r=\dfrac{V_{upper}}{V_{lower}}=5.0$.
**Step 1: amounts in each phase.** The mass of enzyme in the upper phase is $C_{upper}V_{upper}$ and in the lower phase $C_{lower}V_{lower}$, so
$$\frac{m_{upper}}{m_{lower}}=K\,r=4\times5=20 .$$
**Step 2: fraction recovered in the upper phase.**
$$\text{Yield}=\frac{m_{upper}}{m_{upper}+m_{lower}}=\frac{Kr}{1+Kr}=\frac{20}{21}=0.952 .$$
Recovery $\approx\mathbf{95\%}$.